Magnetic resonance imaging diagnosis of intervertebral disc disease and myelomalacia in an American black bear (Ursus americanus)

A 23-yr-old black bear (Ursus americanus) was examined because of paralysis of unknown duration. The precise onset of clinical signs was unknown as a result of seasonal torpor. The bear was immobilized and transported to a university veterinary teaching hospital for further evaluation and treatment. Radiography revealed increased mineral opacity and ventral bridging across vertebral segments T8-11. Magnetic resonance imaging demonstrated dorsal and ventral compression of the spinal cord at T8-9. Given the bear's advanced age, the unknown duration of spinal cord compression, unknown presence of deep pain perception, and thus an unknown prognosis for surgical success, euthanasia was elected. Postmortem examination revealed severe spondylosis deformans from T7 to L3 and dorsal extradural extruded disc material in the area of T8-9. Histopathology demonstrated the dorsal horns of the spinal cord at T9 were replaced by foamy macrophages extending into the dorsal and lateral funiculi of the white matter compatible with focal, severe, chronic myelomalacia. This is the first report of intervertebral disc disease and myelomalacia diagnosed using MRI in a large carnivore.